Synthesis And Charaterization Of Fluorene-Based Blue-Emitting Materials

In recent years, Organic light-emitting materials and devices have attracted more and more research attentions since they have the potentials to use in large-area flat-panel displays and lighting. As the need of full color displays is growing, it is necessary to get red-, green-and blue-emitting materials. Compared with red-and green-emitting materials, blue-emitting materials still have some problems such as poor color purity and imbalance of carrier transporting.Anthracene and fluorene are taken as the blue-emitting materials or the building blocks of blue emitters all the time. They have attracted much attention due to their high fluorescent quantum yield and ease to be modified. However neither of them has good color purity nor stable thermal stability. Both of them are easy to recrystallize and have low glass transition temperature. This situation didn't change until the appearance of oligomer light-emitting materials such as oligo-fluorenes.In this thesis, based on the merits of enthracene and fluorine as building blocks of luminescent molecules and the advantages of small molecular light-emitting molecules over the luminescent polymers, we designed and synthesized fluorene-or bifluorene-based novel molecules A and B by introducting naphthalylanthracene-10-yl into the terminal sides of fluorene chain. Furthermore, in order to tune the emitting wavelength into deep-blue or violet region, we chose triarylsubstituted boron as the core and introduced fluorene and bifluorene as the periphery groups to constructed novel light-emitting molecules C and D. All these four novel molecules were reported for the first time. They were characterized by 1H NMR and MALDI-TOF-MS spectra.The photophysical properties of these four compounds were investigated by means of UV-Vis absorption and fluorescence spectroscopy. A and B emit blue fluorescence with the maximum emission peaks at 429 nm and 436 nm, while C and D in deep-blue or violet range with peaks at 389 and 394 nm. The frontier molecular energy levels were measured and calculated by the cyclovoltametry technique together with "absorption edge " technique. The ionized potential (IP) and electron affinity (EA) were calculated as 5.63eV,1.98eV for C and 5.74eV,2.38eV for D. All these preliminary data implied that compound A and B are potential blue fluorescent materials, and C and D are potential host materials used in doped blue light-emitting devices due to their high excited state energy.